This invention relates to automatic test systems for testing multiple pin electronic components.
In automatic test equipment for the testing of integrated circuits, pin electronics interface circuits are coupled to the pins or other nodes of an electronic device being tested. Through the pins, stimuli signals are supplied to the device under test, and output signals from the device under test are detected and measured. Usually, the stimuli signals represent logic states or analog voltages or currents which are desired to be impressed on the pins of the device under test as a parallel pattern, with the resulting output signals checked in parallel.
Interface circuits of the test equipment function as an interface between the computer controlling the test system and the individual pins of the device under test. The interface circuits receive reference voltages and digital data from other circuits in the test system, and then through drivers associated with each interface circuit switch these voltages or data onto desired input pins of the device under test under control of a program stored in the test system computer. Correspondingly, the interface circuits receive voltages or data from output pins of the device under test and supply that data to a comparator circuit which compares the signal received with the proper response stored in the program of the test system computer.
Memories and registers are used to store the various information needed to provide a test pattern to multiple pins. For instance, the data itself to be provided to the pin is stored as well as the timing information for that data, i.e., the pulse width and beginning and end of pulse times. Typically, a number of data words are stored in a memory or register with each bit of that word corresponding to a different pin. A large number of such words are required in order to generate a sophisticated test pattern. The bits for a particular pin will vary since different pins will have different functions, i.e., some pins will be input pins, others will be output pins, and others will be control pins, etc. If the pattern for an individual pin needs to be varied for some reason (such as for an upgraded version of an integrated circuit having different pin locations, different pin locations between a die and an encapsulated chip, etc.) then the memory and registers need to be written over for the entire group of pins since each bit applied to the pin to be changed is but one bit of a word which applies to all of the pins.